The present invention relates to a plastic material closure member for a container, having a gripping portion, and a substantially cylindrical sealing portion adjacent thereto, and which is preferably intended as a closure means for bottles or tubes.
The main problem in all threadless plastic material closures, in contrast to screw closures, resides in the provision of ready opening and closing of the sealing portion of the closure member in a container neck which is difficult to open and tightly fitting, apart from the extremely slight annular adhesion about the bead portion in the container neck. The positional movement of this sealing portion in threadless plastic material closures is only possible in the distribution of the force in various directions with transmission of the forces on to the inner sealing portion. In all known hermetically sealing threadless closures, the sealing portion is made of relatively rigid and hence hardened plastic material. Therefore this sealing portion as such is substantially inflexible and in the uppermost region of attachment to the container neck is practically unmovably connected to the horizontally mounted, non-displaceable walls directly over the end face of the container. This lateral upper most blocking is therefore, especially at the beginning, the greatest problem during opening of a threadless closure, particularly since this uppermost laterally non-displaceable region in its inflexibility for opening or loosening of the tightly fitting sealing portion requires considerable effort to effect vertical movement of the sealing portion to overcome this region. More especially, even with closures having a rigid sealing portion and only a minimal lateral displaceability, such closures may only be inserted into the neck of a container by the use of maximum effort with straddle and rocking movements, since no direction-controlling pre-centering in the lowermost region of the sealing portion is provided.
This partially uppermost lateral blocking of the sealing portion is moreover also disadvantageous in consideration of the external and internal container neck tolerances. Moreover, crown-top closures for beverage bottles are known which after the filling of the bottles are placed thereon and by means of a tool are so deformed that the edge portions engage positively around a bead formed on the bottle orifice, whereby the bottles are tightly sealed. For opening such bottles numerous tools have been developed, whereby during the opening procedure the edge portions of the closure are so deformed that the latter cannot be used a second time with the same closure effect on the container. This is especially of considerable disadvantage when it is not intended to empty the whole contents of the bottle.
Furthermore, closures for bottles have been proposed which are made of rubber or soft plastic material and which due to their considerable resilience can be inverted over the orifice of the bottle. Since the tolerance limits in bottle necks are relatively large, it frequently happens that the known closures made of soft plastic material perfectly seal bottles having a lip or bulge within the upper tolerance limit, but can only be removed with considerable effort, or that bottles having a lip or bulge within the lower tolerance limit may in fact very readily be removed but provide no hermetic sealing effect. Moreover, attaching such closures to a container neck is not quite simple inasmuch as there are no provisions made to center the closure itself. Closures are also known which have relatively thin sealing part walls in which insertion and removal is relatively easy, but which, however, no longer ensure a hermetic seal.